This invention relates to pressure sensitive one-way valves, and in particular pressure sensitive one-way gas release valves that may be used to automatically release gas pressure built up within a vessel or container.
A variety of different products have a tendency of releasing or emitting gas after they have been placed within a sealed package, container, or vessel. For example, roasted coffee beans have a tendency to release a significant quantity of carbon dioxide following the roasting process, much of which is often released after the roasted coffee has been placed within a sealed container. Should the container or packaging be devoid of any mechanism to allow for the release of built up gas pressure, the walls of the container will have a tendency to expand outward, and depending upon their integral strength, could potentially rupture and fail. Where the container does not rupture a build up of gas can cause a bulge or expansion in the container""s walls making it unattractive from the perspective of a consumer, and also presenting difficulty for the retailer who attempts to maximize the use of retail shelf space. To accommodate the build up and evolution of gases in such circumstances others have proposed the placement of relief valves within the walls of the packaging or container to permit excessive amounts of gases to be slowly bled off, and to prevent the otherwise deleterious effects of an expanding package or container.
In most circumstances, the packaging or container within which a product is placed for transportation and retail sale (particularly in the case of food products) must be relatively inexpensive in order to gain market acceptance. The necessity for inexpensive packaging has resulted in the majority of prior developed valves or pressure release devices being of a relatively simplistic nature, designed primarily from the perspective of allowing built up gas within a container to be bled off. Most often the ability of the valve to function as a one-way valve only, and to prevent the ingress of air from the exterior environment into the sealed packaging or container, is an incidental feature. Many prior existing valve structures provide only a minimal degree of security against the possibility of air travelling backwardly through the valve and into the packaging. For many products incidental contact with air that may seep back through a gas release valve is not of significant concern. However, in other instances any contact with air whatsoever can have a serious effect on the quality and characteristics of the products. For example, roasted coffee that comes into contact with air will quickly oxidize tending to give the coffee a bitter taste. The ingress of air into a sealed and packaged product may also introduce water vapour and/or bacteria into the product that could cause fungal growth or spoilage.
Further, many existing relief valve structures are designed to open at a very low differential pressure between gas within the container and the outside atmospheric pressure. The simplicity and structure of such valves normally causes them to open upon a minimal increase in internal gas pressure. However, where the container packaging is sufficiently strong there can sometimes be an advantage gained by maintaining a higher internal gas pressure. For example, once again with reference to roasted coffee beans, it has been determined that the flavour and aroma of roasted coffee is enhanced if it is allowed to remain in contact with carbon dioxide and aromatic gases that evolve from it following roasting. Maintaining the gas pressure within the container above atmospheric will also have the added benefit of helping to prevent the ingress of environmental air back through the valve and into the seal container.
The invention therefore provides a pressure sensitive one-way valve that helps to address a number of the deficiencies in prior existing devices. The invention provides such a one-way valve that permits the release of built up gas from within a sealed container or package while at the same time preventing or limiting the ingress of air through the valve and into the container or package. The valve is also of a structure that permits the maintenance of a higher than atmosphere internal gas pressure within the container or package where such is desired.
Accordingly, in one of its aspects the invention provides a pressure sensitive one-way valve to control the release of pressurized gas from a sealed container wherein the sealed container has at least one venting aperture therein, the valve comprising a first layer of flexibly resilient material having an upper surface and a lower surface, at least the periphery of said lower surface of said first layer adhered to the outer surface of the container with at least a portion of the interior of said lower surface of said first layer separable from the outer surface of the container, said separable portion of said lower surface of said first layer and the portion of the outer surface of the container adjacent thereto forming an expansion chamber therebetween, said expansion chamber in communication with said venting aperture through said container such that passage of gas through said venting aperture causes expansion of said expansion chamber, said expansion chamber having a gas release aperture extending therethrough permitting the release of gas from said expansion chamber; and, a second layer of flexibly resilient material at least partially covering said first layer with a portion of said second layer adhered to said first layer and a portion of said second layer separable from said first layer, said separable portion of said second layer and the portion of said first layer adjacent thereto forming a gas exiting passageway, said gas exiting passageway in communication with said gas release aperture extending through said expansion chamber, such that expansion of said expansion chamber exerts a lifting force upon said second layer causing said separable portion between said first and said second layers to diverge thereby opening said gas exiting passageway and permitting the flow of gas from the venting aperture in the container through said expansion chamber, through said gas release aperture extending through said expansion chamber, into said gas exiting passageway, and out of said valve into the environment.
In a further aspect the invention provides a pressure sensitive one-way valve to control the release of pressurized gas from a sealed container, the valve comprising a substrate of material adhered to a portion of the outer surface of the container and having extending therethrough one or more apertures aligned with one or more venting apertures extending through the container; a first layer of flexibly resilient material having an upper surface and a lower surface, at least the periphery of said lower surface of said first layer adhered to said substrate layer with at least a portion of the interior of said lower surface of said first layer separable from said substrate layer, said separable portion of said lower surface of said first layer and the portion of said substrate layer adjacent thereto forming an expansion chamber therebetween, said expansion chamber in communication with said venting aperture through said container and said aperture through said substrate layer such that passage of gas through said venting aperture causes expansion of said expansion chamber, said expansion chamber having a gas release aperture extending therethrough permitting the release of gas from said expansion chamber; and, a second layer of flexibly resilient material at least partially covering said first layer with a portion of said second layer adhered to said first layer and a portion of said second layer separable from said first layer, said separable portion of said second layer and the portion of said first layer adjacent thereto forming a gas exiting passageway, said gas exiting passageway in communication with said gas release aperture extending through said expansion chamber, such that expansion of said expansion chamber exerts a lifting force upon said second layer causing said separable portion between said first and said second layers to diverge thereby opening said gas exiting passageway and permitting the flow of gas from the venting aperture in the container through said expansion chamber, through said gas release aperture extending through said expansion chamber, into said gas exiting passageway, and out of said valve into the environment.